On Tuesday 06 October 2009, Gene Heskett wrote: [huge snip about strange noises] > >Just for grins, I'm going to haul my scope out there and see what I find, > and I'll report back. Curiosity bumps need rubbed and scratched you know.
Back from the shop. I wasn't able to get a extension lead to that star point in my lashup, the closest I could get was the chassis of the stepper motors psu, about 30" of 14 gauge wire away. Just waving the probe around I was able to find the short un-shielded sections between where the shielding of the motor cables stops and the motors, a fair amount of noise that was pretty much gone by the time I was 6" of air away. And my running spindle has about 250 volts of combined noise and power when connected directly to it. The best pickup I could get without connection was about 15 volts with the probe laying against the cable for about 3". That seems fairly noisy, but I can't hear it but very faintly on an AM radio 7 feet away, listening to our local AM'er after daytime hours when he has to reduce to 50 watts at sundown. He plays a mix of county and bluegrass that time of the night. Other neighborhood noises are worse than the spindle motor. Hooked onto the z sled, or to the machine frame, was all the same, and about 4.5 volts of noise was generated by the xylotex, but it was very fast, all settled and quiet well within a microsecond, the majority of it in the first 15 nanoseconds. I am inclined to think that I was looking at the 3 foot ground lead acting as an antenna because I got an identical display when checking the chassis of the psu. Long ground leads can do some real funkity stuff in the less than a microsecond time frames. Noise that you can see, and which lasts much longer than a microsecond, probably should be run down and fixed. But I didn't see anything to worry about. I should probably shield the spindle motor lead but haven't found a shielded cable rated for line voltages and up. Haven't looked all that hard either TBT. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) The NRA is offering FREE Associate memberships to anyone who wants them. <https://www.nrahq.org/nrabonus/accept-membership.asp> Nothing can be done in one trip. -- Snider ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
